Diffraction through Mesh - Physics Demonstrations - Diffraction through Mesh | Physics Undergraduate Labs

This demonstration uses a Class IIIb laser. Do not aim the laser toward student seating. The reflection shield prevents backscatter from reaching students' eyes -- do not remove or reposition it while the laser is on. Wear protective eyewear whenever the laser is active after initial alignment.

Purpose

Laser light through circular apertures (0.04 and 0.08 mm) and mesh screens produces Fraunhofer diffraction patterns, demonstrating light's wave nature. Students observe Airy patterns and two-dimensional grating patterns, and verify the inverse relationship between aperture size and pattern size.

$Green laser diffraction pattern from mesh showing complex multi-directional array of bright spots against dark background$

$Green laser diffraction pattern with cross-shaped symmetry showing bright central core and regular horizontal and vertical arrays of spots$

$Leybold diffraction slide labeled "0.04 0.08mm CIRCULAR APERTURES DIFFRACTION PATTERNS" mounted in metal slide holder on adjustable carriage$

Figure 1: Diffraction pattern from a mesh screen showing a complex multi-directional spot array, reflecting the two-dimensional periodicity of the mesh structure.

Figure 2: Square mesh diffraction pattern showing the characteristic cross-shaped spot array. Spot spacing is inversely related to the mesh spacing.

Figure 3: Leybold diffraction slide with 0.04 mm and 0.08 mm circular apertures, mounted in the slide holder on the adjustable carriage.

Optical Slider

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Polished Steel Plate

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Horizontally Adjustable Optical Slider

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2 in 4 Slot Slide Holder

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Safety Warnings

Danger: Class IIIb Laser Hazard

Purpose